Variable-pitch gear



July 3, 1928.

C. C. BRADBURY VARIABLE P11-GH GEAR A Filed March 18, 1926 `Patented July 3, 1928.

UNITEDN STATES PATENT oFFicE. L

CLIFFORD c. imnnnunY, or cimiiacoii,V ILLrNors.

` VARIABLE-FITCH GEAR.

Application led March 18, 1926. Serial No..95,543.

My invention relates Ito variable pitch gears having particular application to the operation of a'plurality of condensers in a.

radio receiving set. i

The object ofthis invention is to provide ready means for changing the pitch of gears In tuned radio frequency receivers. it is.

desirablefthat several timing condensers be moved or rotated simultaneously underthe inuence of a single adjusting member. It has been found difficult Ato manufacture condensers which originally .have and retain exactly thesarne capacity for corresponding positions of rotor and stator.` Furthermore, i

itis extremely difficult to construct the im pediencies which are connected parallel with the condensers sothat the tuned circuits of several condensers and several impediencies willbe tuned exactly alike. for like `settings of the condensers throughout the entire range .ofpositions of therotors of the condensers with` respect to the stators thereof.

My invention contemplates` `means for slight-ly `adjusting the pitch of the operating gears of one or `more of the condensers so 'that all of the condenser rotors may be adjusted to the most accurately tuned positions atvarious `frequencies by means which will bring the `condenser parts to the same relative position whenever the parts are returned to theposition in which the'setting has been made. The invention also contemplates means `whereby the setting of the `pitch for oneposition will have no ejiect upon the pitch at positions remote` from .the position at which a settingr is being made.

My iiiventionalso kcontemplates the use of a coiled spring asa gear whereby the coils ot the spring may be slightly flexed either toward or `from one another as they enter the teeth ,of the meshing gear so that even if the pitch `,of the spring ,gearis not exactly the saine as that of the meshing gear, the convolutioiis of the spring will nevertheless enter between the teeth of the meshing gear, this structure obviating the necessity of a loose fit between the gears which would, of course, result ininaccuracy of relative positions between the two gears, depending upon whether the driver was rotating in a clockwise or a couiite`r-clockwise direction.

which made up.

Myinvention isill'ustrated in theaccompanyin'gdrawing in which: 'j Fig'l shows the general application of the invention to a condenser tuned radio frequency receiver. j

Fig. 2 isa plan of two of the condenser units shown `in Fig. 1.

Fig. 3 isa Msection through a gear wheel principle showing the construction `oiE the wheel. j j

Fig. Ll is an elevation of one of the gear adjusting mechanisms.

Fig. 5 is a `section talren on the line 5-5 j of Figa; j Fig. c is an outline of the blank from the gear supporting wheels are rljhe gear carrying pulleys 10 maybe formed of a pair of punchings 11` and 1Q fastened together by means of eyelets 13 and suitably mounted upon `a `shaft 14. The puncliings 11 and 12 are lprovided with a `plurality of ears 16 and 17 between slots in which a plurality of screws 1,8 are mounted.

These screws maybe made from ordinary p wood screws and whether `so yconstructedor otherwise contain threads of the saine gen` eral shape` and character as the threads of ordinary wood screws. These screws 18I are positioned around the portions lof the pulleys 10 through which it is desired `to make changes inthe gear adjustment. They may be continued through the entire circumference of the pulleysor through a part thereof where changes are desired. A coil of spring wire 20 is wound about the pulleys 10,1 the ends of .the spring being united as at Q1, if complete rotation ofthe gear is not desired, or by any othersuitable means,4` such as welding, brazing or soldering, ii coinpleterotation of the pulleys is desired. l

The springs 2O are normally stretched or opened just suiiciently that the inner con- 'volutions `mesh with the threads on the screws 18. The distance between convolutions at the outer part or' the springs will, of course, be slightly greater thanin the inner part where the springs engage the screws. By rotating one or more of the screws by means of a screw driver the spring convolutions willbe crowded in one direction or the other, depending upon the direction of adjustment of the screw to alter the relative position of the spring and pulley in the region of the particular screw adjusted.

The idling gears 24 pivoted on studs 25 ion mesh with the main driving gear 26 which may be rotated by the hand wheel. 27, thus driving the gears 10 which are rigidly secured to their respective shafts 14.'

Then this invent-ion is applied to a radio receiving set having three condensers, the pulleys 10 are tightened upon the shafts 14; by means ot nuts E28, or by other suitable means, at substantially the correct positions for vproper tuning on sending station, the frequency'of which is such as'to occupy a soniewhat central position on .the scale. Alito-r a crude adjustment has been made by slipping the Vshafts 14rwithin the hubs of the wheels 1() and finally clamping the wheels 10 on their shafts 14V by means of a screw driver, the particular screws 18 which are positioned most nearly adjacent the idlers 24 are adjusted until the most accurate tuning' is secured. The hand wheel27 is then rotated until other stations occupying positions remote from the central position of the dial can be heard and screw driver'adjustments again made of the screws 18 which, under these latter conditions, lie most nearly opposite the idler wheels 24. By making an accurate adjustment for as many positions of the dial as there are screws 18 the receivingset will be accurately tuned at all of the exact positions at which adjustments have been made. Ordinarily the amount by which the receiving set may be out of tune for positions lying between these adjustments are so small as to be negligiblesince the spring will, assume an average pitch between screw adjustments if during the use of the radio receiving set to which this invention is applied one or more of the condensers changes through atmospheric dampness or dryness. Corrections for these changes can be made by adjustment of the screws similar to the adjustments similarly made. Y i

It is to be understood that this invention is susceptible of modilications without departing from the spirit or Vscope of the invention.

What I claim is:

1. A gear wheel or sector comprising grooved pulley, a coiled spring lying within the groove of said pulley, the convolutions of said spring forming the cogs of the gear wheel or sector and means for shifting a portion of the spring along the groove of the pulley.

the spring from sliding around the support-V ing member and for varying the distance between certain of the convolutions.'Y Y

4.-. A variable pitch gear comprisingsupporting member, thread screws rotatably mounted about the periphery of saidsupporting member, a coiled spring lying about the periphery of said vsupporting member and havin its convolutions in registry with the threas of said screws, whereby said coiled spring maybe shifted tangentially of said supportin member by the rotation of said screws.

5. A member adapted to .be engaged by i gear teeth comprising a coil spring provided with a plurality of convolutions, a support for said spring and means-for moving some of the convolutions Without affecting the rcmainin g -convolutions 6.111 combination, a driving means provided with gear teeth, a driven wheel provided with a spring rim adapted to act as gear teeth, and means for shifting a portion of the spring rim to vary the relative position of the driving means to the driven wheel. Y

7. In combination, a pairrof inter-meshing gears, atleast one-of said gears being formed by the convolutions of a spring,;and means' for compressing or separating certain of said convolutions whereby the distancebetween convolutions is increased on one side of said means and decreased-on the other side of said means, the springv being sulficiently flexible to adapt* itself to the otherV gear whereby the convolutions may be slightly flexed either toward or vfrom one another as they enterthe teethof the meshmg gear. v

In witness whereof, I hereunto subscribe my name this 16th day of March, 1926.

CLIFFORD BRADBURY. 

